Flammable Citrus Peel

This demonstration shows how limonene, a hydrocarbon found in the outer layer of citrus peels, can be ignited to produce a small burst of flame and can also react with latex balloons due to its solvent properties.

1. Cut a small piece of orange or lemon peel.
2. Light a candle and hold the peel above the flame to gently warm it.
3. Squeeze the peel sharply toward the flame to release limonene vapor; observe the brief burst of flame as the vapor ignites.
4. Optionally, rub a small amount of orange or lemon peel oil on the surface of an inflated latex balloon and watch how it weakens or pops over time due to the solvent action of limonene on latex.

SPARKS using lemon juice - Hands On Science!:

When life gives you lemons (or oranges) you experiment! | Orange peel explosions - Royal Society of Chemistry:

• Try grapefruit peels to compare how much flame they produce.
• Use a black background to make the combustion flash more visible.
• Test the effect of different natural oils on balloons to compare solvent strength.

• Wear safety glasses to protect eyes from flame and splashing oils.
• Perform the experiment away from flammable materials.
• Do not hold the peel directly in the flame for long periods to avoid burns.
• Use good ventilation to avoid inhaling smoke or fumes.

• Why does orange peel oil ignite when squeezed near a flame? (Because limonene is a hydrocarbon vapor that burns readily in air.)
• What structural feature of limonene makes it similar to cyclohexane? (Both contain a six-membered ring of carbon atoms.)
• Why does limonene weaken or pop balloons? (Because it dissolves the latex polymer, breaking down its structure.)
• What does this tell us about the relationship between natural and synthetic organic compounds? (They often share similar molecular building blocks, such as isoprene units.)